As external memory apparatuses used for computer systems, semiconductor memory apparatuses such as an SSD (Solid State Drive) equipped with a non-volatile semiconductor memory such as a NAND type flash memory (hereinafter, simply referred to as a NAND memory) have attracted attention. In comparison with a magnetic disc apparatus, the semiconductor memory apparatus has advantages in high speed, light weight, and the like. Herein, the NAND memory has a structure capable of erasing data at one time, which is stored in a plurality of memory cells called blocks. However, it is known that the NAND memory has an upper limit in the number of rewrite times.